Expanded nk cells

ABSTRACT

The present invention relates to expanded NK cells. The NK cells have been expanded ex vivo, are activated and have a cytotoxic phenotype. The cytotoxicity against malignant cells is markedly increased compared to non-expanded NK cells. The invention also relates to a method of treatment.

TECHNICAL FIELD

The present invention relates to expanded natural killer (NK) cellsbeing cytotoxic against malignant cells and a method of treatment ofmalignant disease.

BACKGROUND ART

NK cells are cytotoxic lymphocytes that lyse certain tumor and virusinfected cells without any prior stimulation or immunization. NK cellsare also potent producers of various cytokines, e.g. IFN-γ, TNF-α,GM-CSF and IL-3. Therefore, NK cells are also believed to function asregulatory cells in the immune system, influencing other cells andresponses.

In humans, NK cells are broadly defined as CD56⁺CD3⁻ lymphocytes. Thecytotoxic activity of NK cells is tightly controlled by a balancebetween the activating and inhibitory signals from receptors on the cellsurface. A main group of receptors that inhibits NK cell activation arethe inhibitory killer immunoglobulin-like receptors (KIRs). Uponrecognition of self MHC class I molecules on the target cells, thesereceptors deliver an inhibitory signal that stops the activatingsignalling cascade, keeping cells with normal MHC class I expressionfrom NK cell lysis. Activating receptors include the naturalcytotoxicity receptors (NCR) and NKG2D that push the balance towardscytolytic action through engagement with different ligands on the targetcell surface. Thus, NK cell recognition of target cells is tightlyregulated by processes involving the integration of signals deliveredfrom multiple activating and inhibitory receptors.

Several strategies have been used to enhance NK cell responses totumors. Cytokines are used in the treatment of some human cancers and NKcell differentiation and activation is affected by cytokines such asinterleukins (e.g. IL-2, IL-12. IL-15, IL-18 and IL-21). The effect ofIL-2 administration on activation and expansion of NK cells in cancerpatients have been assessed in several trials with mixed outcomesdepending on type of tumor and the conditions used for IL-2administration. One example of cellular therapy is the NK cell-mediatedkilling of leukaemia cells which is based on NK cell alloreactivity.

Multiple myeloma (MM) is a plasma cell neoplasm characterized by theclonal proliferation of plasma cells in the bone marrow (BM). Themalignant cells are associated with the synthesis of monoclonalimmunoglobulin and a high incidence of osteolytic bone lesions. Thedisease accounts for about 2% of all cancer deaths and nearly 20% ofdeaths caused by hematological malignancies. Although allogeneic stemcell transplantation occasionally cures these patients and drugs likethalidomide, lenalidomide and bortezomib have improved outcome,high-dose chemotherapy followed by autologous stem cell transplantation(ASCT) still appears to be the best treatment for patients up to 65-70years of age. However the great majority of patients with MM areincurable due to the persistence of minimal residual disease. Thus,novel methods for complementing or improving current treatments areneeded.

In order to use NK cells in adoptive immunotherapeutic strategies, theavailability of functionally active NK cells on a clinical scale iscrucial. Clinical trials that have been performed using autologous NKcells were hampered by the fact that the cell dose was inadaptable tothe demands of clinical trials. Therefore, the development of protocolsfor large-scale generation of NK cells is important to evaluate thepotential of NK cell-based therapeutic protocols. Examples of reportsthat deal with ways of expanding and culturing human NK-cells are U.S.Ser. No. 10/242,788 and WO 2006/052534.

Human ex vivo expanded NK cells would be favorable candidates forimmunotherapeutic approaches against malignant disease if they couldtarget tumor cells.

Aims of the Invention

One aim of the invention is to provide expanded and active CD56⁺CD3⁻ NKcells.

Another aim of the invention is to provide expanded CD56⁺CD3⁻ NK cellsthat are cytotoxic against cells of malignant disease.

Yet another aim is to provide a method of treatment of a malignantdisease.

SUMMARY OF THE INVENTION

The present invention relates to ex vivo expanded natural killer (NKcells) that can be used for immunotherapy of tumor cells, the NK cellsshowing no significant cytotoxicity against normal cells. The NK cellsaccording to the invention are ex vivo expanded and active cells havingthe phenotype CD56⁺CD3⁻. This phenotype is specifically toxic againsttumor cells. Upregulation of at least one activating receptorcontributes to the cytotoxic activity of the expanded NK cells. In oneembodiment the invention relates to a composition comprising the NKcells according to the invention.

In another embodiment the present invention relates to a method oftreatment of a malignant disease wherein NK cells according to theinvention or a composition according to the invention are/isadministered to a patient with a malignant disease, or a patientundergoing autologous stem cell transplantation for cancer, or a patientwith a malignant disease following allogeneic stem cell transplantation,or a patient with haematological malignancies, or a patient with solidtumors, in a pharmaceutically effective dose.

DISCLOSURE OF THE INVENTION

Before the present invention is described, it is to be understood thatthe terminology employed herein is used for the purpose of describingparticular embodiments only and is not intended to be limiting, sincethe scope of the present invention will be limited only by the appendedclaims and equivalents thereof.

It must be noted that, as used in this specification and the appendedclaims, the singular forms “a,” “an,” and “the” include plural referentsunless the context clearly dictates otherwise.

Also, the term “about” is used to indicate a deviation of +/−2% of thegiven value, preferably +/−5%, and most preferably +/−10% of the numericvalues, where applicable.

Given their strong cytolytic activity and the potential forauto-reactivity, natural killer (NK) cell activity is tightly regulated.In order to kill cells with a missing or abnormal MHC class I expressionthe NK cells need to be activated. NK cells must receive an activatingsignal which can come in a variety of forms, the most important of whichare cytokines, Fc receptors, activating and inhibitory receptors. In thecontent of the present invention the term “activated NK cells” refers toNK cells that have received an activating signal, thus being capable ofkilling cells with deficiencies in MHC class I expression.

In the content of the present invention the term “NK cell expansion”relates to the culturing of NK cells that go through a series of celldivision and thus expand in number of cells present in the culture. Theterm “expanded NK cells” relates to NK cells obtained through NK cellexpansion. More specifically, in one embodiment the term “expanded NKcells” relates to a polyclonal group of chronically activated CD56⁺CD3⁻cells, expanded in a specific cGMP grade environment and cGMP grademedium.

In the content of the present invention the term “upregulation ofreceptor” relates to the increase in receptor density per cell.

In the content of the present invention cells that have a “cytotoxicphenotype” relates to cells that are toxic, i.e. they induce the deathof other cells such as, but not limited to, tumor cells, infected cellsor cells that are otherwise damaged or dysfunctional. Cytotoxic cells ofthe present invention are mainly toxic to tumor cells. The cytotoxicityof NK cells towards other cells can easily be measured, for example, bytraditional cell counting before and after exposure to the NK cellsaccording to the invention. Such methods are well known to a personskilled in the art. Examples of suitable methods are, but not limitedto, fluorescent cell counting assay, immunofluorescent cell countingassay, cell viability assay, and flow cytometry-based cytotoxicityassay.

In the context of the present invention the term “effector cell” relatesto a cell that performs a specific function in response to a stimulussuch as cells in the immune system. In one embodiment effector cells area type of lymphocytes that are actively engaged in secreting antibodies.Non-limiting examples of effector cells are NK cells, T cells andNK-like T cells

Ex vivo expansion and reinfusion of natural killer (NK) cells topatients afflicted with a malignant disease offers a new potentiallyinteresting therapeutic approach to combat such a disease. Aprerequisite for this is the possibility to expand and use NK cells thatmeet the demands of clinical trials. The present inventors havesurprisingly shown that ex vivo expanded NK cells can be used forimmunotherapy of tumor cells that often express varying levels of MHCclass I molecules, the NK cells showing no significant cytotoxicityagainst normal cells.

Accordingly, the present invention relates to ex vivo expanded andactivated natural killer cells having the phenotype CD56⁺CD3⁻. The NKcells according to the invention are expanded, active and have aphenotype cytotoxic against tumor cells, preferably autologous tumorcells. The NK cells can be obtained from any conventional source and arepreferably derived from peripheral blood, bone marrow, cord blood, celllines or cytokine stimulated peripheral blood. NK cells can, forexample; be expanded from a sample of peripheral blood mononuclear cells(PBMCs). PBMCs are a mixture of monocytes and lymphocytes; bloodleucocytes from which granulocytes have been separated and removed. Theculture conditions are outlined below in “Experimentals”. According tothe present invention the NK cells should be expanded for at least about5 days, preferably not less than about 10 days, more preferably not lessthan about 15 days and most preferably not less than about 20 days.Already after 5 days the NK cells can show anti-tumor activity.

Furthermore, in one embodiment of the invention the NK cells accordingto the invention should be expanded at least about 100 fold, preferablyat least about 200 fold, more preferably at least about 400 fold, morepreferably at least about 600 fold, more preferably at least about 1000fold and even more preferably at least about 1500 fold.

The activating pathway of NK cells also includes a series of differentreceptors. Activating receptors do not directly signal through theircytoplasmic tail, but instead associate non-covalently with othermolecules containing ITAMs (immunoreceptor tyrosine-based activationmotifs), that serve as the signal transducing proteins. Thus, accordingto one embodiment of the invention the ex vivo expanded and activated NKcells have an upregulated expression of at least one activatingreceptor. Non-limiting examples of activating receptors are: CD16(FcγRIII), CD25 (IL-2Rα), CD27, CD28, CD69, CD94, CD122 (IL-2Rβ), CD161,CD226 (DNAM-1), 2B4 (CD244), CD314 (NKG2D), KIR2S, KIR3S, NCRs (naturalcytotoxicity receptors) such as NKp30, NKp44, and NKp46, CD85H (ILT-1)and IFN-α/βR. Preferably said at least one activating receptor isselected from the group consisting of 2B4, CD8, CD16, CD 27, CD226,NKG2D, NKp30, NKp44 and NKp46. In one embodiment of the presentinvention the at least one activating receptor is 2B4 or CD226.

The NK cells according to the present invention exhibit higherdegranulation activity compared to non-expanded NK cells. Thedegranulation activity can be estimated through the determination of theCD107a expression. CD107a surface expression correlates closely withdegranulation and release of cytotoxic granules. Degranulation asmeasured by CD107a expression correlates to cytotoxic activity of aneffector cell, such as an NK cell. The method of determiningdegranulation activity through the determination of CD107a expression iswell known to a person skilled in the art. See, for example, Alter G,Malenfant J M, Altfeld M. CD107a as a functional marker for theidentification of natural killer cell activity. J Immunol Methods. 2004;294:15-22.

The change in receptor expression can be calculated by mean fluorescenceintensity (MFI) ratios:

MFI_(dayX)/MFI_(day0)

where x is the number of days of expansion of the NK cell.

When the MFI for day X samples is higher than for day 0, the MFI ratiowill be higher than 1, which indicates the relative extent ofupregulation in that receptor. Thus, a MFI ratio of e.g. 1.5 would meana 50% of upregulation of a specific receptor. The calculation of MFIratios is well known to persons skilled in the art.

According to one embodiment of the present invention the at least oneactivating receptor is upregulated by at least about 50%, preferably atleast about 75, more preferably at least about 100% and most preferablyat least about 200%.

According to another embodiment of the invention the NK cells have adown-regulated expression of at least one receptor, such as aninhibitory receptor or a chemokine receptor (e.g. CCR7). Non-limitingexamples of inhibiting receptors are inhibitory killerimmunoglobulin-like receptors (KIRs). Further non-limiting examples ofinhibiting receptors are GL183, KIR2DL1, Lir-1, NKB1, and NKG2A. It ispossible that none inhibitory receptor can be downregulated in somepatients, one inhibitory receptor downregulated in some patients andmore than one in some patients. Thus, in one embodiment of the inventionthe NK cells according to the invention can have an upregulatedexpression of at least one activating receptor and a down-regulatedexpression of at lest one receptor. In another embodiment the NK cellsaccording to the invention can have an upregulated expression of atleast one activating receptor and a downregulated expression of at lestone inhibitory receptor.

According to another embodiment of the present invention the expandedand activated NK cells have at least about 100% increased cytotoxicitycompared to non-ex vivo expanded NK cells. Preferably at least about150%, more preferably at least about 200% and most preferably at leastabout 400% increased cytotoxicity compared to non-expanded NK cells. Nonexpanded NK cells relates to freshly isolated NK cells and short-termactivated NK cells. In the context of this invention the expression“short term activated” means NK cells that have been expanded over nightonly.

The increased cytotoxicity of the expanded and activated NK cells canalso be an effect mediated by an upregulation of a combination ofreceptors. Thus, in yet another embodiment the present invention relatesto expanded and activated NK cells having an upregulated expression ofmore than one receptor. Thus, recognition of the target cell by NK cellscan involve a combination of receptors that synergistically deliveractivating signals.

Another embodiment of the present invention relates to a compositioncomprising the expanded and active NK cells as described above. Inaddition to the NK cells, a composition according to the invention mayalso contain any suitable physiological buffer, such as, but not limitedto, phosphate buffered saline. Suitable physiological buffers are wellknown to the skilled person. Other substances, such as, but not limitedto cytokines such as IL-2 and its derivatives, immunomodulatory drugsand proteosome inhibitors, that increase the effect of the administeredcells can also be added to the composition or administered separately.In one embodiment the composition also contains lower levels of othercells. Non-expanded PBMCs usually contain a mixture of different cells,for example, NK cells (CD56⁺CD3⁻), NK-like T cells (CD56⁺CD3⁺) and Tcells (CD56⁻CD3⁺). After expansion NK cells are the dominating cell typein the culture but also other cell types can be present in the expandedculture.

The NK cells according to the invention can also be administered or usedin combination with other cancer therapies, such as, but not limited to,surgery, radiation and cytotoxic drugs.

Several experimental studies have shown that NK cells can eliminatecancer cells. The results of the study underlying the present inventionsuggest that ex vivo expanded and activated cells have a promisinganti-tumor potential compared to resting NK cells. Thus, the presentinvention also relates to NK cells being cytotoxic against tumor cells,said tumor cells preferably being autologous tumor cells. Autologoustumor cells refer to cells that are reimplated in the same individual asthey came from, i.e. the donor and the recipient are the same person.Allogeneic tumor cells, on the other hand, refers to cells taken fromdifferent individuals of the same species, i.e. geneticallynon-identical individuals. Two or more individuals are said to beallogeneic to one another when the genes at one or more loci are notidentical.

The NK cells according to the present invention are cytotoxic againsttumor cells, said tumor cells being selected from, but not limited to,the group consisting of haematological tumors or malignancies and solidtumors or malignancies. Haematological tumors or malignancies includetypes of cancer that affects the blood, the bone marrow and the lymphnodes. In particular the NK cell according to the invention is cytotoxicagainst cells of lymphoma (e.g. Hodgkin's disease and non-Hodgkin'slymphoma), multiple myeloma (MM), and leukaemia (e.g. acute lympoblasticleukemia, acute myelogeneous leukaemia, chronic myelogeneous leukaemia,chronic lymphocytic leukaemia, hairy cell leukaemia). Examples of solidtumors are, but not limited to, hepatocellular tumors, gastrointestinaltumors (such as colon tumors), ovarian tumors, renal tumors, lung tumorsand pancreatic tumors. In one particular embodiment of the presentinvention the NK cells are cytotoxic against multiple myeloma cells.

Since large numbers of activated NK cells now can be produced and usedin the setting of adoptive immunotherapy, the present invention alsorelates to a method of treatment. In leukemia patients autologous exvivo expanded and activated NK cells might be helpful for treatment ofminimal residual disease (MRD) after autologous stem celltransplantation. According to the invention it would be advantageous toadminister autologous ex vivo cultured NK cells, either prophylacticallyor therapeutically, to patients undergoing autologous hematopoietic stemcell transplantation for diseases such as multiple myeloma which have ingeneral a poor prognosis with high incidence of progressive disease posttransplant. Ex vivo expanded NK cells of donor origin can be used forthe treatment of recurrent malignant disease following allogeneic stemcell transplantation. Autologous NK cells can be administered, eitherprophylactically or therapeutically, to patients undergoing autologousstem cell transplantation for cancer. Other ways of using autologous NKcells is for ex vivo purging of malignant cells in the harvest, fortreatment of patients with hematological malignancies, and as a cellulartherapy for solid tumors.

Another embodiment of the invention is therefore a method of curative orprophylactic treatment, wherein expanded, activated and cytotoxic NKcells with the phenotype CD56⁺CD3⁻, as described above, are administeredto patients with a malignant disease, or to a patient with a malignantdisease following allogeneic stem cell transplantation, or patientsundergoing autologous stem cell transplantation for cancer, or patientswith hematological malignancies, or patients with solid tumors, in apharmaceutically effective dose. A patient can also be treated with theinventive method in order to prevent recurrence of a malignant disease.

In another embodiment of the inventive method a composition comprisingthe NK cells is administered to patients with a malignant disease orpatients undergoing autologous stem cell transplantation for cancer, orto a patient with a malignant disease following allogeneic stem celltransplantation or patients with hematological malignancies, or patientswith solid tumors, in a pharmaceutically effective dose. The compositionaccording to the invention can also be administered to a patient inorder to prevent recurrence of a malignant disease.

Examples of malignancies/tumors that can be treated with the inventivemethod are outlined above.

In the inventive method a sample (e.g from peripheral blood, bonemarrow, or cord) is taken from a patent afflicted with a malignantdisease. In one embodiment the patient has been treated withconventional cancer therapies but the treatment has been unsuccessful orthe malignancy has recurred. The method can also be a prophylactictreatment, for example, to prevent recurrence of a malignant disease.Before culturing the cells (e.g. PBMCs), they are purified and separatedaccording to methods well known for the skilled person. The cells arethereafter ex vivo expanded as outlined above and in the “Examples”.Subsequently, the expanded cells are administered to the patient. Thepatient is thereafter carefully followed-up in order to determine if thepatient has responded well to the treatment and to determine if thetreatment is to be repeated. Samples can, for example, be taken fromblood, bone marrow and or urine for follow-up of the treatment atregular time intervals.

In the inventive method the NK cells are preferably are ex vivo expandedfor at least about 5 days, preferably not less than about 10 days, morepreferably not less than about 15 days and most preferably not less thanabout 20 days before administration to the patient.

In another embodiment the NK cells have been expanded at least about 100fold, preferably at least about 200 fold, and more preferably at leastabout 400 fold, preferably at least about 600 fold, more preferably atleast about 1000 fold and even more preferably at least about 1500 foldcompared to day 0 of expansion, before administration to a patient.

The inventive method can be performed once or repeated several times. Inone embodiment the NK cells according to the invention are administeredto the patient about 1-10 times, preferably about 1-7 times, morepreferably about 1-5 times and most preferably about 1-3 times. Theadministration route can be any suitable way of administration wellknown to the skilled person for example, but not limited to;intravenous, intraperitoneal and intratumoral administration. The dosagecan be the same in all administrations or for example high in the firstadministration(s) and than lower in subsequent administrations.

Administration, alone or in combination with the NK cells of theinvention, of subcutaneous IL-2 or its derivatives as well asimmunomodulatory drugs such as, but not limited to, thalidomide orproteosome inhibitors such as, but not limited to, bortezomib, mayfurther increase the effect of administered cells.

The features of the ex vivo expanded and activated NK cells to be usedin the method of treatment are as described above for the NK cellsaccording to the invention.

BRIEF DESCRIPTION OF THE FIGURES

The invention is further described in the description, examples andclaims with reference to the attached figures in which:

FIG. 1 shows expansion dynamics of blood and bone marrow samplesobtained from seven multiple myeloma patients and cultured for 20 daysunder identical conditions. Bulk cells in culture expanded to a total of511 fold (A). Initial OKT-3 treatment lead to an increased percentage ofT cells in the culture during the first five days of culture followed bya decrease after withdrawal of OKT-3 (B). The subsequent increasecontinued until finally NK cells dominated in the culture (C). Resultsare shown as means +SD.

FIG. 2 shows changes in the receptor expression patterns of NK cellsfollowing expansion and activation. Representative data (Patient 5)showing comparative phenotyping of day 0 (grey) and day 20 (white) cells(A). Each patient's MFI ratios (·) of day 20 to day 0 as well as themedians (−) of seven patients were plotted for each receptor (B). Thedashed line shows MFI ratios=1 which indicates unaltered receptorexpression during the expansion period. Values above the line (MFIratio>1) indicate upregulation and below (MFI ratio<1) denotedownregulation.

FIG. 3 shows the results from the cell mediated cytotoxicity assays. NKcell cytotoxicity against K562 cell line was measured by the standardchromium release assay and flow cytometry based cytotoxicity assay (A).The flow cytometry based cytotoxicity assay demonstrates an increasedcytotoxicity of expanded NK cells (day 20) against autologous MM cellscompared to freshly isolated NK cells (B). Expansion and activation ofthe cells did not affect the cytotoxicity against autologous normal BMcells (B). Representative data (Patient 5) is shown to demonstrate theanalysis procedure (C).

FIG. 4 shows blocking of activating receptors on NK cells. The resultsare shown as mean 522 inhibition+SD (N=3).

FIG. 5 shows CD107a mAb based degranulation assay against primary MMcells. Representative data (Patient 5) demonstrating the expression ofCD107a on NK cells after contact with the NK sensitive K562 cell lineand autologous MM cells (A). Comparison of CD107a expression on day 0, 5and 20 NK cells upon contact with 519 autologous MM cells (B). Theresults are shown as percent CD107a cells +SD (N=3).

MODE(S) FOR CARRYING OUT THE INVENTION

The invention will now be further described in the experiments outlinedbelow wherein efficient ex vivo NK cell expansion from PBMCs (peripheralblood mononuclear cells) of Multiple Myeloma (MM)+patients usingclinical grade components is demonstrated. Furthermore, the ability ofthese NK cells to kill autologous tumor cells is shown. These datasuggest the possibility of using autologous ex vivo expanded NK cellsfor immunotherapy of MM.

EXPERIMENTAL Patients and Acquisition of Patient Material

Peripheral blood and bone marrow (BM) samples from seven newly diagnosedpatients at different stages of MM were included in the study. Thepatients were followed at the Department of Hematology, KarolinskaUniversity Hospital Huddinge, Stockholm, Sweden. The study was approvedby the local research ethics committee. Informed consents were obtainedfrom all patients. Patients' characteristics at the time of blood and BMsampling for the study are given in Table 1.

TABLE1 Patient characteristics at the time of blood and bone marrowsampling for the study. MM Stage Patient* Age Gender (Durie &Salmon) MMType 1 41 Male IIIB IgG-λ 2 80 Male IB IgG-λ 3 80 Male IIIB Lightchain-λ 4 75 Female IIA IgG-λ 5 66 Female IIB IgG-λ 6 53 Female IA IgG-κ7 64 Male IIB Light chain-κ *All the patients included in this studywere diagnosed in the first half of 2006 and had not yet started anytreatment regimen at sampling time.

PBMCs as well as BM mononuclear cells (BMMCs) were isolated by gradientcentrifugation, using Lymphoprep (Axis-Shield, Oslo, Norway). PBMCs andBMMCs were washed twice with phosphate-buffered saline (PBS) (Gibco,Grand Island, N.Y., USA), and cell viability was assessed by Trypan blueexclusion. To avoid inter-experimental variability, PBMCs and BMMCs weredirectly frozen in human serum albumin (Baxter) containing 6% DMSO(Wak-chemie medical, Germany) for subsequent phenotyping andcytotoxicity experiments.

Example 1 Ex Vivo Expansion of NK Cells from PBMCs

Material & Methods: The culture conditions for the expansion ofcytotoxic cells have previously been optimized on PBMCs from healthyindividuals (Carlens et al., Hum. Immunol. 2001; 62:1092-1098). Briefly,PBMCs were initially thawed and cultured in T25 flasks (TPP,Trasadingen, Switzerland) at a concentration of 0.5×10⁶ cells/ml inCellGro SCGM serum-free medium (CellGenix, Freiburg, Germany) with theaddition of 5% human serum (Biowhittaker-Cambrex, Md., USA) and 500 U/mlrhlL-2 (Proleukin®, Chiron Corporation, Emeryville, Calif., USA). Forthe first 5 days, the medium was further supplemented with anti-CD3antibody (Orthoclone OKT-3, Ortho Biotech Inc., Raritan, N.J., USA) to afinal concentration of 10 ng/ml. On day 5 of culture, theOKT-3-containing medium was washed out, and fresh medium with IL-2 (500U/ml) and 5% human serum was added. The cultures were then replenishedwith fresh medium every other day throughout the culture period. Totalcell numbers were assessed by staining cells with Trypan blue dye ondays 0, 5-6, 9-10, 14-15, and 20 of culture. Absolute cell counts werecalculated by multiplying the total number of cells with the percentageof these subsets determined by flow cytometry. To prevent contactinhibition of cell growth, the cells were transferred to bigger flaskswhen necessary. The final products were evaluated for purity, viabilityand phenotype.

Results: In order to study whether it is possible to expand NK cellsfrom MM patients using GMP grade components, cultures of PBMCs fromseven patients with MM were established. At the start of the culture(day 0), the mean percentage of NK cells (CD56⁺CD3⁻) was 11% (range:7-17%) whereas T cells constituted 57% (range: 36-81%). NK cellexpansion approached log-linearity after an initial non-proliferativephase of about five days. By day 20, the total cell population hadexpanded on average 511-fold (range: 123-1545) (FIG. 1A) and, of these,NK cells had expanded on average 1625-fold (range: 502-2658) (FIG. 1B).Due to the relatively greater expansion of NK cells compared to theother cell types, NK cells dominated the culture towards the end of theculture period, reaching on average 66% of the cells by day 20 (FIG.1C). The percentage of NK-like T cells (CD56⁺CD3⁺) did not changesignificantly during the culture period (day 0: 14%, day 20: 18%), whilethe percentage of T cells (CD56⁻CD3⁺) declined following withdrawal ofOKT3 at day 5, decreasing to an average of 14%. These results show thatNK cells from MM patients can be expanded efficiently ex vivo by usingthe present 20 day culture approach.

Example 2 Flow Cytometry Based Phenotyping of NK Cells and NK Ligands onMultiple Myeloma (MM) Cells

Material & Methods: The cell phenotype and expansion dynamics ofsubpopulations were analyzed by flow cytometry on days 0, 5-6, 9-10,14-15 and 20 of culture using standard procedures with fluorochromeconjugated mAbs against the following surface antigens CD3, CD14, CD38,CD56 and CD138.

Day 0 and day 20 cells from all patients were subjected to a moredetailed immunophenotypic analysis. To avoid inter-acquisitionvariability, all frozen samples were simultaneously thawed for adetailed phenotypic characterization of CD56⁺CD3⁻ (NK) cell subset byflow cytometry. This panel included fluorochrome conjugated mAbs againstthe following surface antigens: CD2 (RPA-2.10), CD3 (UCHT-1), CD4 (SK3),CD7 (M-T701), CD8 (HIT8a), CD14 (MOP9), CD16 (3G8), CD19 (HIB19), CD25(M-A251), CD27 (M-T271), CD38 (HIT2), CD56 (B159), CD57 (NK-1), CD161(DX12), CD183 (3D12), CD184 (12G5), CD195 (2D7/CCR5), CD197 (1C6/CXCR3),CD226 (DX11), NKB1 (DX9), LFA-1 (HI111), CD62L (DREG56), CD69 (FN50) andCD138 (MI15) purchased from BD Biosciences, San Jose, Calif., USA; CD48(MEM102) from Biosource AB, Stockholm, Sweden; CD158B1/B2,j (GL183),CD244 (2B4) (C1.7), NKG2D (ON71), NKp30 (Z25), NKp44 (Z231), NKp46(BAB281), LIR-1 (HP-F1), Valpha24 (C15), Vbeta11 (C21) from BeckmanCoulter Inc., Fullerton Calif., USA; NKG2A (131411), NKG2C (134591),KIR2DL1 (143211), KIR2DL3 (180701) from R&D Systems, Minneapolis, Minn.,USA.

All antibody stainings for flow cytometry were done according to thefollowing protocol. Fc receptors were blocked by incubation with 1 μghuman IgG per 105 cells for 15 minutes on ice. The cells were thenwashed once with PBS and incubated with appropriate amounts of antibodyat 4° C. for 30 minutes followed by another wash with PBS. For bothpanels, LIVE/DEAD Fixable Red Dead Cell Stain (Invitrogen, Carlsbad,Calif., USA) was used for dead cell exclusion according to themanufacturer's instructions. Briefly, 1 μl of dye was applied to 1×106cells resuspended in 1 ml of PBS and incubated on ice for 30 minutes.The labeled cells were then washed with PBS and fixed in 4% PFA prior todata acquisition. Cells were analyzed by nine-color flow cytometry(CyAn™ ADP LX, Dako A/S, Glostrup, Denmark) calibrated with CompBeads™and appropriate isotype controls (BD Biosciences). The acquired datawere analyzed with Dako Cytomation Summit software versions 4.2 and 4.3(Dako A/S) and FlowJo software version 7.2 for PC (Tree Star Inc.,Ashland, Oreg., USA) setting appropriate SSC/FSC gates around thelymphocyte population and using LIVE/DEAD Fixable Red Dead Cell Stainnegative cells. From the lymphocyte gate, NK cells were gated as theCD56⁺CD3⁻ population. NK-like T cells and T cells were gated asCD3+CD56+ and CD3+CD56− populations respectively. MM cells were gated asCD38+CD138+. In each sample a minimum of 105 cells was analyzed.

For each cell surface receptor analyzed, mean fluorescence intensity(MFI) values were calculated for day 0 and day 20 samples. To estimatethe change in receptor expression, MFI ratios were calculated(MFlday20/MFlday0) for each receptor. When the MFI for day 20 sampleswas higher than for day 0, the MFI ratio was higher than 1, whichindicated the relative extent of up regulation in that receptor.Likewise, an MFI ratio below 1 was interpreted as down regulation in theexpression of that receptor.

Results: To characterize the final expansion product with respect to thestarting material, a detailed flow cytometric analysis was undertaken(representative data of one patient is shown in FIG. 2A). For eachreceptor analyzed, MFI values were calculated in samples from day 0 andday 20 cultures and used their ratio (MFlday20/MFlday0) as an indicatorof the change. FIG. 2B illustrates the MFI ratios of all patients forall receptors analyzed as well as the median values. Briefly, in thefinal product, the inventors observed a significantly upregulatedexpression of the following activating receptors: 2B4, CD8, CD16, CD27,CD226, NKG2C, NKG2D, NKp30, NKp44 and NKp46. The inhibitory receptorsKIR2DL3 and LIR-1 were also upregulated. The chemokine receptor CCR7 wassignificantly down-regulated whereas CXCR3 was markedly upregulated. Nosignificant changes in the expression levels of CD2, CD7, CD57, CD62L,CD69, CD161, LFA-1, GL183, KIR2DL1, NKB1, NKG2A, CCR5 or CXCR4 wereobserved.

Example 3 Evaluation of Cell-Mediated Cytotoxicity

Material & Methods: The cytotoxic capacity of NK cells before and afterexpansion was evaluated in vitro with a standard 4 hour 51 Cr-releaseassay against NK-sensitive K562 cells. Because the 51 Crrelease assay isnot suitable for primary MM cells 16-18, a flow cytometry based cellmediated cytotoxicity assay was used.

For the 51 Cr-release assay, K562 target cells were labelled with 100μCi of 51Cr for one hour at 37° C., washed twice with PBS, andresuspended in 1 ml of RPMI medium. A total of 3×104 target cells in 100μl RPMI medium was placed in triplicates into V-bottom 96-well platesand incubated for 4 hours with 100 μl of effector cells at appropriateconcentrations to obtain effector:target ratios from 1:3 to 10:1.Aliquots of supernatants were then counted using a Packard CobraAuto-Gamma 5000 Series Counting System (Meriden, Conn., USA). Thepercentage of specific 51Cr release was calculated according to theformula: percent specific release=[(experimental release−spontaneousrelease)/(maximum release−spontaneous release)]×100.

For the flow cytometry based assay, autologous MM cells or K562 controlswere labelled with TFL4 reagent of the CytoToxiLux-PLUS kit (OncolmmuninInc., Gaithersburg, Md., USA) according to the manufacturer'sinstructions. 5×104 target cells were placed in tubes together withdifferent amounts of effector cells to obtain effector:target ratiosfrom 1:3 to 10:1 in a final volume of 300 μl RPMI medium and incubatedat 37° C. for 4 hours. The cells were then washed once with PBS.Following Fc receptor blockade with IgG (1 μg/105 cells) on ice for 20minutes to avoid antibody-dependent cellular cytotoxicity, the cellswere incubated with appropriate amounts of fluorochrome conjugated mAbsagainst CD3, CD34, CD38, CD56 and CD138 at 4° C. for 30 minutes. Afterwashing with PBS, the cells were resuspended in 500 μl of PBS containing5 μg 7-aminoactinomycin D (7-AD; Invitrogen, Carlsbad, Calif., USA) andincubated in the dark for an additional 15 minutes at 4° C. before dataacquisition by nine-color flow cytometry. Cytotoxicity was assessedaccording to the following formula: percent killing =[(experimentaldeath-spontaneous death)/(maximum death-spontaneous death)]×100.

To compare cytotoxicity of short term activated and expanded cells, day5 cells from three patients were also tested for cytotoxicity againstK-562 cell line and primary autologous myeloma cells.

For blocking experiments, effector cells were preincubated at 4° C. for30 minutes with 10 μg/ml of isotype controls or the mAbs against thefollowing receptors: 2B4 (C1.7)19, CD226 (DX11)20, NKG2C (134522), NKG2D(1D11)21, NKp30 (Z25)22, NKp44 (Z231)22, NKp46 (BAB281)22, and CD27(1A4)23.

Results: The inventors next investigated the cytotoxic activity of exvivo expanded NK cells against a standard NK target cell line, K562.Cytotoxicity against K562, measured by a flow cytometry-basedcytotoxicity assay and confirmed by a standard 4-hour chromium releaseassay, was markedly increased by day 20 NK cells when compared to day 0and day 5 cells (FIG. 3A). At a 10:1 effector to target cell ratio, 62%of the K562 targets were killed by the day 20 NK cells whereas day 0 andday 5 cells killed only 8% and 29% of K562 targets, respectively, at asimilar effector to target ratio.

In an in vivo immunotherapy approach, the present NK cells would only beuseful if they are able to target autologous MM cells. The inventorsthus assessed cytotoxicity against autologous MM cells by a flowcytometry based assay. At day 20, marked cytotoxic activity of NK cellsagainst autologous MM cells was observed whereas both day 0 and day 5cells showed no or only low levels of cytotoxicity (FIG. 3B). At a 10:1effector:target ratio, 61% of autologous MM cells were killed by day 20cells (representative data of one patient is shown in FIG. 3 c).Notably, no significant cytotoxicity against non-MM (CD138-) cells wasobserved. Ex vivo expanded NK cells show increased cytotoxicity againstautologous MM cells.

To determine the relative contributions of different activatingreceptors on autologous MM cytotoxicity, effector cells werepreincubated with blocking antibodies against several individualactivation receptors, or their combinations, and then co-incubated withautologous MM cells. Cytotoxicity was partially inhibited by blocking2B4 (60% inhibition), CD226 (DNAM-1; 53%), NKG2C (48%), NKG2D (49%),CD27 (50%), NKp30 (57%), NKp44 (55%), and NKp46 (59%) (FIG. 4). Thisindicates that several activating receptors may contribute to MMcytotoxicity in line with current knowledge of receptor synergy forinduction of cytotoxicity. Thus, the cytotoxicity against autologous MMinvolves target cell interaction with activating NK cell receptors.

Example 4 Analysis of NK Cell Degranulation

Material & Methods: NK cells were coincubated with target cells at aratio of 1:1 in a final volume of 200 μl in round-bottomed 96-wellplates at 37° C. and 5% CO₂ for 6 h. Fluorochrome-conjugated anti-CD107amAb or the corresponding IgG1 isotype control was added at theinitiation of the assay. After 1 h of coincubation, Monensin (GolgiStop,Becton Dickinson) was added at a 1:100 dilution. Surface staining wasdone by incubating cells with anti-CD3 and anti-CD56 mAbs for 30 mins onice. The cells were then washed, resuspended in PBS and immediatelyanalyzed by flow cytometry.

Results: In order to better pinpoint the active population within thefinal expansion product showing cytotoxicity against autologous MMcells, the inventors shifted focus from MM cell lysis to effector cellactivation by analyzing the surface expression of CD107a on differentsubpopulations upon contact with MM cells. CD107a expression correlatesclosely with degranulation and release of cytotoxic granules.Approximately 30% of Day 20 NK cells expressed CD107a on the cellsurface on contact with K562 cell line. Similar degranulation wasobserved against autologous MM cells (representative data of one patientis shown in FIG. 5A). Analysis of expanded cells showed that NK cellswere the main degranulating population following challenge withautologous MM cells (FIG. 5B). Thus, autologous MM cells triggerdegranulation of ex vivo expanded NK cells.

Discussion (Example 1-4)

Although previous reports suggest that cytokine activation of NK cellsmay lead to a better recognition of MM cells, MM cells are considered tobe resistant to lysis by resting and short term activated autologous NKcells. Similar to the immune system defects mentioned above, thisresistance has been explained by NK cell dysfunctions in MM patientsincluding impaired NK cytotoxicity and increased levels of soluble IL-2receptors as well as decreased expression of a number of activatingreceptors compared to healthy controls. The results indicate thatexpansion and/or long term activation of NK cells may reverse thispotential dysfunction, since it was paralleled by induction of surfaceexpression of CD107a and cytotoxicity of autologous MM. Based onassessment of induction of degranulation measured by expression ofCD107a, it was concluded that expanded NK cells are the major effectorcompartment exerting autologous anti-MM activity under the presentexperimental conditions. Within the course of the present studies theinventors also phenotyped the expanded NK cells. This allowed acomparison of day 0 and day 20 NK cells. Since a balance of activatingand inhibitory signals regulates NK cell function, optimal NK celleffector function is expected to occur in situations where theexpression of activating NK cell receptors is adequate and notsuppressed by inhibitory signals. Reduced 2B4 expression in NK cellsfrom MM patients has been suggested to play a role in the immune escapemechanism of MM expressing its ligand CD4841, however it cannot beexcluded that it might be a consequence of interactions between NK andMM cells. The upregulation of 2B4 after ex vivo expansion is likely onefactor contributing to the cytotoxicity observed against autologous MMcells. Furthermore, NCRs and NKG2D, which presumably take part in therecognition of MM cells by NK cells, are significantly upregulated,suggesting possible pathways for autologous MM cell killing. Theupregulation of CD226 which is a tumor surveillance receptor on NKcells, and a potent inducer of cytotoxicity against many tumor celllines of hematopoetic and non-hematopoetic origin, could also contributeto the increase in cytotoxicity. Furthermore, it has previously beenshown that CD27 NK cells are tightly regulated by inhibitory receptorswhereas CD27 high NK cell subset is more cytotoxic. The upregulation ofCD27 during expansion may also contribute to elevated levels ofcytotoxicity.

Recently published results of clinical trials testing NK cell basedimmunotherapy involve infusion of resting and short-term IL-2 activatedNK cells to patients with malignancies. These trials have shown thatadoptively transferred NK cells are well tolerated. The present resultsshows that the present ex vivo expanded autologous NK cells have apromising anti-MM potential compared to resting or short-term activatedNK cells. The high levels of NK cell expansion using cGMP qualitycomponents is of particular importance in relation to reaching anappropriate infusion dose in settings of immunotherapy.

A concern for the use of activated NK cells, especially in theallogeneic settings, is that they could cause a tissue damagingreaction. The present data shows that the recognition of autologous MMcells by ex vivo expanded NK cells involve a certain degree ofspecificity. The inventors demonstrated that day 20 NK cells lysed MMcells but spared non-MM cells from the same patient.

Although particular embodiments have been disclosed herein in detail,this has been done by way of example for purposes of illustration only,and is not intended to be limiting with respect to the scope of theappended claims that follow. In particular, it is contemplated by theinventor that various substitutions, alterations, and modifications maybe made to the invention without departing from the spirit and scope ofthe invention as defined by the claims.

1. Natural killer (NK) cells that are ex vivo expanded and said expanded NK cells are active and have a CD56⁺CD3⁻ phenotype, said phenotype being cytotoxic against autologous tumor cells.
 2. The NK cells according to claim 1, wherein said NK cells have an upregulated expression of at least one activating receptor.
 3. The NK cells according to claim 2, wherein said activating receptor is upregulated by at least about 50%.
 4. The NK cells according to claim 2, wherein said at least one upregulated activating receptor is a natural cytotoxic receptor (NCR).
 5. The NK cells according to claim 2, wherein said at least one activating receptor is selected from the group consisting of 2B4, CD8, CD16, CD 27, CD226, NKG2D, NKp30, NKp44 and NKp46.
 6. The NK cells according to claim 1, wherein said NK cells have at least about 100% increased cytotoxicity compared to freshly isolated non-expanded NK cells.
 7. The NK-cells according to claim 1, wherein said NK cells have been expanded for at least about 5 days.
 8. The NK-cells according to claim 1, wherein said NK cells have been expanded for at least about 10 days.
 9. The NK cells according to claim 1, wherein said NK cells are cytotoxic against tumor cells, said tumor cells are cells from haematological tumors.
 10. The NK cells according to claim 1, wherein said NK cells are cytotoxic against autologous tumor cells, said tumor cells being selected from the group consisting of cells from multiple myeloma, leukaemia and lymphoma.
 11. The NK cells according to claim 1, wherein said NK cells are cytotoxic against autologous tumor cells, said tumor cells being cells from multiple myeloma.
 12. The NK cells according to claim 1, wherein said NK cells is cytotoxic against autologous tumor cells, said tumor cells being cells from solid tumors.
 13. The NK cells according to claim 1, wherein said NK cells are cytotoxic against autologous tumor cells, said tumor cells being selected from the group consisting of cells from hepatocellular tumors, gastrointestinal tumors, ovarian tumors, renal tumors, lung tumors and pancreatic tumors.
 14. The NK cells according to claim 1, wherein said NK cells exhibit higher degranulation activity compared to non-expanded and activated NK cells as determined by CD107a expression.
 15. A composition comprising NK cells according to claim
 1. 16. Method of curative or prophylactic treatment, wherein NK cells according to claim 1 are administered to a patient with a malignant disease following allogeneic stem cell transplantation, or a patient undergoing autologous stem cell transplantation for cancer, or a patient with haematological malignancies, or a patient with solid tumors, in a pharmaceutically effective dose.
 17. The method according to claim 16, wherein the NK cells are administered to a patient to prevent recurrence of a malignant disease.
 18. The method according to claim 16, wherein the NK cells are ex vivo expanded for at least about 5 days prior to administration to the patient.
 19. The method according to claim 16, wherein the NK cells are expanded at least about 100 fold prior to administration to the patient.
 20. Method of curative or prophylactic treatment, wherein the composition according to claim 15 is administered to a patient with a malignant disease following allogeneic stem cell transplantation, or a patient undergoing autologous stem cell transplantation for cancer, or a patient with haematological malignancies, or a patient with solid tumors, in a pharmaceutically effective dose.
 21. The method according to claim 20, wherein the composition is administered to a patient to prevent recurrence of a malignant disease.
 22. The method according to claim 20, wherein the NK cells are ex vivo expanded for at least about 5 days prior to administration to the patient.
 23. The method according to claim 20, wherein the NK cells are expanded at least about 100 fold prior to administration to the patient. 